Résumé:

The concept of nuclear spin temperature is one of the cornerstones of the nuclear magnetism in solids. It has made possible realisation of the cryogenic cooling into the microKelvin range and observation of nuclear spin ordering in metals and insulators [1]. However, proving its validity for semiconductor nano- and microstructures is challenging due to the lack of techniques capable of precise sensing of weak nuclear magnetisation in a small volume. We develop a method of non-perturbative optical control over adiabatic remagneti- sation of the nuclear spin system in semiconductors and apply it to study nuclear spin thermodynamics in GaAs microcavities. The nuclear spin system is found to exactly follow the predictions of the spin-temperature theory, despite the quadrupole interaction that was earlier reported to disrupt nuclear spin thermalisation [2]. These ndings open a way to deep cooling of nuclear spins in semiconductor structures, with a prospect of realisation of nuclear spin-ordered states for high delity spin-photon interfaces. References [1] A. S. Oja, O. V. Lounasmaa, Rev. Mod. Phys 69, 1 (1997). [2] P. Maletinsky, M. Kroner, A. Imamoglu, Nat. Phys 5, 407 (2009).